Electric clock



March 5, 1935. F. LOEFFLER 1,993,411

ELECTRIC CLOCK FRrrz L oeFF/.ER

INVENTOR.

M42- MA 3 A TTORNEY.

March 5, F LQEFFLER ELECTRIC CLOCK Filed July 14, 1951 2 Sheets-Sheet, 2

IN V EN TOR.

W@ ATTORNEY Patented Mar. 5, 1935 UNITED STATES PATENT OFFICE 8 Claims.

This invention relates to improvements in switching mechanisms particularly adapted for use in electric clocks of the general type disclosed in my copending application Serial No. 484,330, filed September 25, 1930,

The object is the provision of a commutating mechanism or switch, for supplying intermittent electric impulses to a motor, which has few parts, is easy to assemble and in which the contact points are kept clean by wiping action.

The commu'tating mechanism preferably consists of a contact cam having a brush spring pressed into engagement therewith, and a lifting finger adapted to be operated, responsive to turning of the rotor, quickly to lift the brush free from the contact cam.

It is mounted at one side of the motor, preferably the side away from the time unit, so that adjustments and repairs may be effected quickly and easily without separating the two units.

The hereinbefore mentioned and other objects and advantages of my invention will be made clear in the following description and accompanying drawings.

In the drawings, Fig. 1 is a side elevation View, in section, of an electric clock constructed in accordance with my invention.

Fig. 2 is a sectional view taken along line 2-*2 of Fig. 1.

Fig. 3 is a View of a modied form of device wherein the commutating mechanism is entirely insulated from the frame of the motor.

Fig. 4 is a sectional View taken along line 9-9 of Fig. 3.

Figs. 5, 6 and 7 are views showing the commutating mechanism of the motor of Fig. 1, shown in different operating positions.

Referring more particularly to the drawings, reference numeral 1 indicates a frame of nonmagnetic material, which may be made, for eX- ample, of bakelite or other insulating material cast in the proper shape. This frame has an annular groove 2 therein and three sets of projecting bosses 3, 4 and 5, which are perforated to receive holding bolts. Embedded in the center of the frame is a shaft 6 around which are located at equal radial distance, arcuate openings '7. A magnetizing coil 8 is positioned in the annular groove and has interlinked with it a plurality of pole pieces 9 of magnetic material, which are substantially U-shaped in cross-section.

The shaft 6 has journaled thereon at the side opposite to the groove 2, a toothed spider 10 of magnetic material, This spider may have a brass or other antifriction bushing l1 pressed therein at the point of engagement with the shaft. The washer l2 is provided for giving the necessary clearance between the spider and 'the frame. Rotatably mounted on the opposite end 5 of the shaft is a disc 13 of brass or any other suitable material and this disc is spaced from the frame by washer 14. The spider and the disc are xed together by posts 15 which extend through the openings 7 in the frame. These 10 posts may have one end thereof reduced in diameter as shown at 16, and be pressed into corresponding hcles in the spider, and at the other end thereof may be fixed to the disc 13 by screws 17 and 18. I find this manner of connection to gj; be advantageous but the posts might be fixed in position in any other suitable manner, as by riveting, welding or the like. The screw 18 has an integral collar or shoulder 19 spaced a short distance from the head thereof and this shouln 20 der, when the screw is in position, engages the face of the disc 13 and holds it in its proper position as shown in Fig. 2. Another screw 20 similar to 18 is attached to the disc 13 and lifting hook 21 is carried by these screws.

The lifting hook, as shown in Fig. 2, has a pair of holes 26 and 22 therein which are just large enough to take the heads of the screws 18 and 20 respectively and the thickness of the hook is just sufficient to permit it freely to slide between the collars and heads of the screws. The holes 26 and 22 terminate at one side in apertures wide enough to receive the shank of the screws but not the head thereof, so that when the hook is dropped into position over the heads of the screws and moved sidewise it cannot be removed vertically. The hook is held in this position by means of a tension spring 23 which is fastened to the frame at 27 and engages at the other end with a hole in the hook. The extended aperture section 25 ci hole 22 is made arcuate, being on a radius from the center of screw 1S, whereby the hook 21 is permitted to swing around screw 18 as a center against the resistance of spring 23. A second tension spring 27 is hooked around the screw 20 and fastened to the frame at 28. This is an'auxiliary energy storingvspring of the device. The spring 23 likewise acts as an energy storing spring and because of the substantially diametrically opposed position of the two springs, the radial load of them on the bearings of the rotor and shaft 6, is substantially neutralized.

The-hook 2l has a flat face 29 which is substantially radial with respect to the shaft 6 at the center of the rotor. This flat face 29 joins an arcuate portion 30 of the hook formed about the shaft 6 as a center. A contact spring 31 is furnished which is attached at one end to a supporting post 32 molded or'otherwise fixed into the insulating frame. The other end of this contact spring is slotted at 33, as shown most clearly in Fig. 1 and is adapted to receive the end of the lifting hook 21. The spring has at the end of the slot a turned up cam-like finger 34 which serves to engage with the hat face 29 of the hook upon operation of the device. The post 32 is so located with respect to the hook that the spring 31 eX- tends in a direction substantially normal to that of the flat face.

One end of the coil 8 is connected to the post 32 and the other end thereof is connected to a binding post 35 fixed in the frame 1. The disc 13 has fixed to it a cam of silver or other conducting material 36 which is adapted to engage with a brush or contact of a similar material 37 iixed to the end of spring 31. A washer 36A spaces the cam from the disc and both the cam and washer are held in position by the integral collars of screws 18 and 20. The holes i the cam are made slightly larger than the Shanks of the screws, so that the position of the cam can be adjusted relative to contact 37 of spring 31.

The entire working mechanism may be enclosed by a housing 69, for example elliptical in section, as shown in Fig. 2, or of any other ornamental shape. This housing holds the crystal 70 of the clock in position. The crystal may either be clamped between a lip 71 of the housing and pressed against the clock dial 72 as shown at the right hand side of Fig. 1, or it may be forced into a notch 73 in the rim of the housing, and the dial be held in position by a shoulder 74, as shown at the left hand side of Fig. 1. A cover plate 75 closes the rear end of the housing and is held in position by studs 55 and nuts 76 screwed thereon. By taking oir the cover plate 75, the contactor points 36 and 37 andother commutator parts may be adjusted without disturbing the motor parts or the clock unit.

In Figs. 3 and 4 a motor is illustrated wherein the operating circuit is entirely insulated from the rotor and housing of the device, so that the motor may be used on lighting lines or other circuits Wherein it is desired to prevent ground connections. In this modification the earn 89 corresponding to contact cam 36 of the preceding figures, is made of insulating material and engages With a Contact spring 90 by means of which connection is made With the contact spring or brush 3l. The spring 96 has a slot 91 therein which permits the free operation of lifting hook 21 in any possible position thereof, and a contact button 92 is fixed to the spring for engagement with the Contact member 37 of the brush 31. In operation, as the rotor revolves carrying the cam 89 with it the Cain engages the brush 90 lifting it and the brush 31 until the end of the hook slips under the cam portion 34 of the brush thereby lifting the brush free V:trom the flat face 29 of the hook and permitting the hook to slide under the finger, just as described in connection with Fig. 1. The position of cam 89 may be adjusted as described in connection with cam 36 of Fig. l. One end of the coil is connected to brush 31 and the other end thereof is connected to an insulated binding post such as shown in Fig. 6. Current is supplied to the device through brush 90 and the insulated binding post so that no current passes through the rotor, casing, or other metallic parts of the device. It will be noted that due to the approximately parallel relationship of the brushes 31 and 90, a wiping action is made between the contacts 37 and 92 upon lifting motion of the cam 89.

M cttcd of operation-When the electric clock is put into operation, a current of the proper voltage is supplied to it by connecting a source of power to the binding pos 35 and to the casing 69. As soon as this circuit is completed, current passes from the binding post 35 through the coil 6, spring 3l, brush 37, contact 36 and thence through the shaft 6, and over the metallic parts of the mechanism, to housing 69. The coil 8 being energized, a magnetic field is set up, the lines of flux of which thread through the pole pieces 9, thereby causing them to attract the adjacent teeth of the spider 10 and rotate it in a clockwise direction, as viewed in Fig. 2, bringing the teeth more nearly into line with the pole pieces. As the rotor 16 turns against the tension of springs 23 and 27, fiat face 29 of hook 21 engages with the earn surface 34 of spring 31, and prevents the hook troni turning around shaft 6 as a center. 'The result is that the end of the hook adjacent the hat face 29 remains substantially stationary vwhile the other end rotates with the screw 18. On the other hand, the motion of the hook 21 with respect. to the disc 13 and pivot screw 18 is a counterclocltwise rocking motion, as viewed in Figs. 2, disc 13 continues, the contact cam 36 gradually forces the spring upwardly to the position shown in 6. In this position the brush 37 is still contact with the cam 36 so that current still iows through the winding 3, but the cam portion Se of the spring is about to slide over the outer end of fiat face 29 and around the arcuate portion 30 oi the hook. When this point is reached the hoch, which has been held back against the tension of spring 23 by the cam portion 34 striking hat face 29, is quickly snapped ahead to the position shown in Fig. 7, thereby lifting the brush 37 from engagement with the contact cam 36 and breaking the circuit through coil 8. During this rotational movement of the spider 19, the pawl 63 slides over the teeth of ratchet wheel 60 and as soon as the coil 8 is deencrgised, by opening of the contacts 36 and 37, the rotor lO returns to its originel position under the influence of tension springs 23 and 27, the ratchet wheel 60 being carried with it by action of the pawl 68 engaging with the teeth of the wheel. The spring 63 is made relatively weak with respect to the two springs 23 and 27, so that the rotor or spider is permitted to return to its original position against the tension of spring 63. Just as this original position is reachedgthe Contact spring 3l snaps down to the position shown in Figs. 2 and 5, and the various operating steps are repeated in the same manner as already described. The ratchet wheel 6G is prevented from returning to its original position by the holding pawl 107.

Several oscillating cycles of the rotor follow each other in quick succession until the spring 63 is tensioned sufficiently to counterbalance the tension of springs 23 and 27 and prevent the rotor from returning to its original position. When this state is reached, the cominutator parts retain ie position as shown in Fig. 7, the brush being out oit engagement with the cam 36. In the meantime, spring 63 has been driving the escapement, hand and other clock works forming the time unit, and continues to drive these parts. When the tension of spring 63 has been suillciently reduced by driving the clock works, the rotor and 5, 6 and 7. As rotation of the spider 10 and associated commutator parts return to the position shown in Figs. 2 and 5, thereby causing the coil to be energized and the spring 63 tensioned again to such value that the parts are held in the position of Fig. '7, With the contacts open.

Because of the relative difference in the storing capacity of the main drive spring 63 and springs 23 and 27, when the clock is iirst put into operation the main drive spring is tensioned to a plurality of units by successive oscillations of the motor rotor and thereafter is kept tensioned by the storing of one unit at a time, responsive to single oscillations of the rotor. The result of this is that if the supply current of the motor is turned off for a period of time greater than that necessary for the clock works to expend one unit of energy, the clock will continue to operate until all of the units of energy are used up and the spring 63 is totally unwound, or until current is again supplied to the motor, whereupon the driving spring 63 is immediately tensioned to its full operating value. The teeth of the ratchet wheel 60 are made relatively fine so that if the voltage applied to the motor is low, the rotor may turn just far enough to open the contacts 36 and 37 and be held in that position by the tension of spring 63. On low voltage therefore, the time between oscillations of the rotor would be small, whereas if a relatively high voltage were supplied to the motor, the turning angle of the rotor would be large and consequently the time between the oscillations thereof would be greater. This feature insures that the device will operate over a relative wide change in supply voltage and furthermore that shock to the parts upon the application of high voltage will be avoided. All of the energy will be taken up by the main driving spring.

The brush 37 should not disengage contact cam 36 until it is lifted free therefrom by the point of the hook 21 sliding quickly under the cam portion 34 of the spring 31. This insures that a quick break will be made and wearing of the contact points by minute arcs prevented. Adjustment of the Contact cam relative to the brush can be made by loosening the screws 18 and 20, and moving the cam to a new position. Because of the rotary motion of the contact cam with respect to the brush, a wiping action is produced which tends to keep the contact surface clean and in eiiicient Working condition.

When it is desired to repair the commutator or to replace any of its parts, the hook 21 thereof may be removed merely by unhooking the springs 23 and 27, moving the hook sidewise until the heads of screws 18 and 20 register with the openings 26 and 22 in the hook, and then lifting the latter vertically free from the screws. By taking out the screws 18 and 20, the contact cam 36 may be removed. All of these parts are located at the back side of the whole clock unit vand so may be repaired or adjusted without disturbing the rest of the motor unit, or the time unit. The entire motor unit may be removed merely by unscrewing the nuts 56 and lifting the motor free from the studs fixed to the time unit. The shaft 6 withdraws from the sleeve 77 carrying the hands and from the bearing plate 51, leaving all of the parts in their proper position to receive the same shaft or that of a replacement motor unit. The quill 57 and the parts carried by it may be removed with the motor said member, a brush spring pressed into engagement with said contact cam, and a lifting finger ivotally mounted on said member and adapted to oscillate around a point eccentric of said center, said finger having a hook portion for engaging said brush and preventing rotation of said finger with said member, and a curved portion adapted to raise said brush free of said cam upon rotation of said member.

2. A commutator comprising a rotatable member, a contact cam fixed to said member, a brush spring pressed into engagement with said cam, a lifting finger rochably mounted on said member eccentrically of the center of rotation thereof and adapted to engage said brush, and resilient means for holding said finger in a normal position with respect to said member.

3. An electric switch comprising a rotatable member, a fixed contact spring and a lifting hook, and means for pivotally supporting said lifting hook on said rotatable member and eccentrically thereof, said lifting hook having a fiat face substantially radial to the center of rotation of said member, which serves to engage said contact spring, said spring being arranged to extend in a direction substantially normal to said at face.

4. A device in accordance with claim 3 wherein said contact spring is provided with a curved cam surface at its point of engagement with said lifting hook.

5. A commutating mechanism according to claim 3 wherein said rotatable member carries a Contact cam arranged to be engaged by said contact spring.

6. A commutating mechanism comprising a rotatable member having a pair of studs eccentrically positioned thereon, and a lifting hook, said lifting hook having a pair of holes therein adapted to receive the ends of said studs, one of said openings being elongated and curved around a radius from the center of said other opening.

'7. A commutating mechanism comprising a rotatable member having a pair of headed studs thereon and a lifting hook, said lifting hook having a pair of holes therein large enough to receive the heads of said studs and each of said openings having an extended section of a size smaller than the head of said studs, and spring means for holding said hook so that said studs are engaged in said extended sections.

8. In a switching mechanism for electric motor driven clocks, contacts for controlling the motor circuit, and means for mounting said contacts near the densest part of the free magnetic flux of the motor.

FRITZ LOEFFLER. 

